Main Street Capital Corporation Quarterly report pursuant to Section 13 or 15(d)

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - $ / shares		3 Months Ended			210 Months Ended
SUBSEQUENT EVENTS (Details) - $ / shares	Nov. 08, 2024	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Mar. 31, 2025
Subsequent Event [Line Items]
Increase in common stock, dividends, per share, declared, monthly (as a percent)				4.20%
Forecast \| O 2024 Q4 Dividends
Subsequent Event [Line Items]
Common stock, dividend, per share, declared (in dollars per share)			$ 0.735
Forecast \| O 2025 Q1 Dividends
Subsequent Event [Line Items]
Common stock, dividend, per share, declared (in dollars per share)		$ 0.75
Forecast \| O 2025 Q1 Covering Period Since October 2027 Initial Public Offering and Including Supplemental Dividend
Subsequent Event [Line Items]
Common stock, dividend, per share, cash paid (in dollars per share)					$ 43.675
Subsequent Event \| O 2025 Q4 Supplemental Dividends
Subsequent Event [Line Items]
Common stock, dividend, per share, declared (in dollars per share)	$ 0.30
Subsequent Event \| O 2024 M10 Dividends
Subsequent Event [Line Items]
Common stock, dividend, per share, declared (in dollars per share)	0.245
Subsequent Event \| O 2024 M11 Dividends
Subsequent Event [Line Items]
Common stock, dividend, per share, declared (in dollars per share)	0.245
Subsequent Event \| O 2024 M12 Dividends
Subsequent Event [Line Items]
Common stock, dividend, per share, declared (in dollars per share)	0.245
Subsequent Event \| O 2025 M1 Dividends
Subsequent Event [Line Items]
Common stock, dividend, per share, declared (in dollars per share)	0.25
Subsequent Event \| O 2025 M2 Dividends
Subsequent Event [Line Items]
Common stock, dividend, per share, declared (in dollars per share)	0.25
Subsequent Event \| O 2025 M3 Dividends
Subsequent Event [Line Items]
Common stock, dividend, per share, declared (in dollars per share)	$ 0.25